I had a similar problem on mine. Actually two problems. The button was really sticky, which made it difficult to press in the angled fashion it was designed to move. My button seemed slightly oversized to start, or perhaps mounted slightly askew -- in any case, after a month it abraded somewhat so it's now easier to push.
The second problem was with the arbor nut/screw, a piece one normally doesn't touch. Once I got the pad off for the first time (with difficulty), I couldn't mount any other except for the one it came with. When I brought it to the dealer we loosened the screw ever so slightly, which fixed the issue and allowed other pads to be mounted.